Practical Torrefaction of Forest Waste for Conversion into Clean Fuel for Coal-fired Power Plants

Coal-fired electric power generating plants are under increasing pressure to reduce CO2 and other toxic emissions. However, using alternative fuels, such as solid biomass as a greenhouse gas neutral fuel, requires substantial plant modifications. In addition, burning biomass contributes to slagging and fouling of the plants' furnaces. Soil mixed in with the forest waste is the primary cause. HM3 Energy has developed an innovative process (trademarked "TorrB") to convert forest waste into fuel briquettes with low soil content. Unlike most pellets and briquettes produced from wood chips, these briquettes behave just like coal; i.e., they can be stored outdoors, are easily pulverized, and their heating value is similar to that of coal. The TorrB process uses torrefaction where the biomass is heated to a high temperature (200-300 degrees C) for a specified time duration in the absence of oxygen. The final product is a solid with a high energy value for use as combustion fuel in coal-fired power plants. This Phase II grant research will focus on developing commercial scale torrefaction equipment and process. HM3 Energy's TorrB torrefaction process and product have demonstrated clear viability as shown in the results of our NIFA-USDA-SBIR Phase I study using a small batch process. By taking the current proven torrefaction process and applying it to a scalable design which utilizes a continuously operating torrefaction system, we will be able to economically produce the large quantities of torrefied biomass required to operate coal-fired power plants. Our approach will be to develop, test and optimize the new torrefier equipment of our own design. When combined with the (waterless) contamination removal methodology developed in Phase I, we will then be ready to apply this knowledge to construction of a full commercial production facility. The potential impacts and benefits of large scale commercial use of torrefied biomass in place of coal are numerous. The forest waste feedstock is renewable and sustainable, and can be obtained from undesirable species (such as western Juniper) present in semiarid regions and through forest thinning and removal of accumulated forest debris - even bug-infested dying trees. By removing the undesired forest waste, the forest ecosystem will be less susceptible to insect and pathogens. There will also be a reduction in the potential for catastrophic forest fires. Overall, the nation's health and environment will be improved by a reduction in coal-fired power plant emissions of carbon dioxide, sulfur dioxide, nitrogen oxides, mercury and other toxic metals present in the coal and coal ash. In fact, America's supply of clean water is threatened by mercury pollution, much of which comes from coal-fired power plant emissions that get into water resources. Replacing coal, the greatest source of CO2, with carbon-neutral biomass fuel in the current installed base of coal-fired power plants could have the greatest impact on green house gases of any mitigation measure. Air quality, as well as the environmental health of water resources and ecosystems in forest, rangeland and farms, could be greatly enhanced.